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video: Implement continuous screen refresh for SmartLCD into mxsfb 

The LCDIF interface doesn't give us any means to do continuous refresh
when driving a SmartLCD. To work this around, we produce a special
circular DMA descriptor, which only writes the HW_LCDIF_CTRL0 register
and sets the RUN bit.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>
Cc: Otavio Salvador <otavio@ossystems.com.br>
Cc: Stefano Babic <sbabic@denx.de>
This commit is contained in:
Marek Vasut 2013-07-30 23:37:54 +02:00 committed by Anatolij Gustschin
parent 9de4b729eb
commit 84f957f80b
1 changed files with 26 additions and 0 deletions
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26
drivers/video/mxsfb.c
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@ -15,11 +15,14 @@
#include <asm/errno.h>
#include <asm/io.h>
#include <asm/imx-common/dma.h>
#include "videomodes.h"
#define PS2KHZ(ps) (1000000000UL / (ps))
static GraphicDevice panel;
struct mxs_dma_desc desc;
/**
* mxsfb_system_setup() - Fine-tune LCDIF configuration
@ -194,5 +197,28 @@ void *video_hw_init(void)
/* Start framebuffer */
mxs_lcd_init(&panel, &mode, bpp);
#ifdef CONFIG_VIDEO_MXS_MODE_SYSTEM
/*
* If the LCD runs in system mode, the LCD refresh has to be triggered
* manually by setting the RUN bit in HW_LCDIF_CTRL register. To avoid
* having to set this bit manually after every single change in the
* framebuffer memory, we set up specially crafted circular DMA, which
* sets the RUN bit, then waits until it gets cleared and repeats this
* infinitelly. This way, we get smooth continuous updates of the LCD.
*/
struct mxs_lcdif_regs *regs = (struct mxs_lcdif_regs *)MXS_LCDIF_BASE;
memset(&desc, 0, sizeof(struct mxs_dma_desc));
desc.address = (dma_addr_t)&desc;
desc.cmd.data = MXS_DMA_DESC_COMMAND_NO_DMAXFER | MXS_DMA_DESC_CHAIN |
MXS_DMA_DESC_WAIT4END |
(1 << MXS_DMA_DESC_PIO_WORDS_OFFSET);
desc.cmd.pio_words[0] = readl(&regs->hw_lcdif_ctrl) | LCDIF_CTRL_RUN;
desc.cmd.next = (uint32_t)&desc.cmd;
/* Execute the DMA chain. */
mxs_dma_circ_start(MXS_DMA_CHANNEL_AHB_APBH_LCDIF, &desc);
#endif
return (void *)&panel;
}